Multiple switch-board



M. G. KELLOGG. .MULTIPLE SWITCH BOARD.

(No Model.)

Patented May 8,1888; 7

N, PETERS, Phmwlilh gmphur. Washingivn, D.

4 UNITED STATES MILO e. KELLOGG, OF HYDE PARK, ILLINOIS.

MULTIPLE SWITCH-BOARD.

SPECIPICATION forming part of Letters Patent N 0.38237 7, dated May 8, 1888;

Application filed August 29, 1887. Serial No. 248,162. (No model.) I 7 To all whom it 11mg; concern.-

Be it known that I, MILO G. KELLOGG, of Hyde Park, Illinois, have invented certain new and useful Improvements in Multiple Switch-Boards for Telephone-Exchanges, of which the following is a full, clear, and exact description, reference being had to the accompanying drawings, forming apart of this specification.

My invention relates to a metallic-circuit telephone-exchange system, and especially to a system in which the subscribers lines are not grounded at the subscribers stations. and are not normally grounded at the .central office; audit consists in a method of testing at any of the boards to determine whether a line is in use at another board, which system I shall describe and claim in detail.

In the accompanying drawings, illustrating my invention, Figure l isa diagram illustrating the main-line apparatus and circuits. Fig. 2 shows a diagram of the operators cordsystem for receiving and answering calls, switching, and clearing out subscribers lines. Fig. 3 shows an operators test system, including a test plug, battery, bell, and connections. Fig. 4 shows a modification of the apparatus and system.

In Fig. 1, A is a sectional view of one switchboard, and A is a sectional view of another switch-board to which the same lines are connected. I place as many boards in the office as are found necessary or desirable, in order to properly answer the calls and make the connections. On each board is a spring-jack or other suitable switch for each line. Each spring-jack has a contact-spring which normally bears on an insulated contact-point and has a contact-piece insulated from the rest of the switch, (except by line-connections,) and is adapted to receive a loop switch-plug, and when the plug is inserted to disconnect the spring from the contact=point (on which it normally rests) and connect the contact-pieces of the plug with the spring and the contactpiece, respectively. In the figure, g g repre" sent the springs of the different switches, h h, the contact-points, and j j the contact-pieces.

\ The plugs D D, (shown in Fig. 2,) when insorted into the switches, operate them as above 'connected with the ground at the central described. The contact-pieces should be, so placed that a test-plug or other switch-testing device may be readily connected with them. Each subscribers circuit'begins, say, at the central oflice, and passes by a wire, which we will call wire No. 1, to the subscribers station, through the station apparatus, and back to the central office by another wire, which we will call wire No. 1". One of the wires-say wire No. l-is connected to all the contact-pieces above mentioned of its switches on the different boards. The other wire passes successively through the contact-points formedby the spring-levers and their corresponding points of its switches on the dilferent boards, passing in each case to thespring first. It is then connected to wire No.18 If an annunciator is used to receive the calls of a line, it is preferable to place it in the circuit of the line after it has passed through thecontactpoints, as above, and before it'passe's from there to the contact-pieces. The lines arenot connected with the ground at the subscribers stations or normally elsewhere; but they are office when they are switched for conversation, as and for the purpose which will here inafter appear.

-Fig. 2 shows a pair of loop switch-plugs with flexible loop-cords adapted to fit intothe spring-jack switches and make the switchingconnections for two lines which are to be connected together for conversation. One of the conductors of the cordis grounded by a branch wire, as shown. It is evident that when one of the plugs is placed in the spring jack switch of one line and the other plug is placed in the spring-jack switch of another line the twoliues are connected together in metallic. circuit and the circuit is grounded at 0 the central office. 1 i I Fig. 3 shows a test-circuit with apparatus for use by an operator at any board. 'It consists, essentially, of a wire with a signal bell and'battery in its circuit, grounded at one end 5 and terminating at the other end in a flexible cord with a plug adapted to be brought into contact with any of the contact-piecesat the board.

'Each operator should have ather board asys roe so I tem of pairs of cords with their plugs, with the necessary switches, telephone, and generator suitably placed and connected, so as to properly conduct the business assigned to her.-

In Fig. 2 only one pair of cords is shown. Others could be added to her system in ways evidentto those skilled in the art. She should also have at her board a test system similar to that described above. For the test-receiving instrument she might use a telephone or other suitable apparatus in the place ofthe bell which is shown.

When an operator at any board desires to test a line to see whether it isin use at another board, she connects her test-plug to the contact-piece at her board of theline to be tested, and if the lineis in use there will be a complete circuit through her test bell and the battery, and the bell will respond and she will know that the line is already in use. The circuit can be traced as follows: Beginning with the ground, thence through the testbell and battery to the testplug, and thence through the contact-piece. and the line back to the ground, (to which the line is temporarily connected while switched for conversation.) If, however, the line is not switched for use, there will be no such complete circuit when the test is made, because the line is disconnected from the ground, and the test-bell will not respond.

It is not a necessity in my system that the lines should be grounded when they are switched for conversation, if the apparatus and connections are modified accordingly. The lines, when switched, may be connectedto a common metallic test circuit or wire, to which are also connected the test-circuits at the different boards. In the modification shown in Fig. 4 the connections are thus made. It is, however, convenient to use the ground as a part of the test-circuit, and I have heretofore described its use.

It is known not to be detrimental to the working of a metalliccircnit telephone exchange to have the metallic circuits grounded at the central office while they are used for conversation, provided they are not then grounded elsewhere, or to have the circuits joined together at one point in each, provided they are not looped together. For these reasons my test system as originally described or as modified'will not effect the successful working of the metallic-circuit system.

The testbattery may be placed in the com.

mon ground-wire or in the common test-wire, should one be used, instead of their being one in t the test circuit of each board after it branches from the ground or the common testwire. In Fig. 4 the test-battery is placed in the common test-wire.

I claim as my invention and desire to secure by Letters Patent- 1. In a telephone-exchange system, two inetallic-eircuit telephone lines normally disconnected from the ground and temporarily connected together for conversation,with their circuit grounded, in combination with a testbell grounded on one side and connected on its other side to a switch-testing device, adapted to be brought into connection with either line for testing, and a battery in the test-circuit between the ground-connection on one side of the bell and the temporary ground-connection of the two lines, substantially as and for the purpose set forth.

2. In a telephoneexchange system, two metallic-circuit telephone lines normally disconnected from the ground and temporarily connected together for conversation,with their circuit grounded, in combination with a testwire grounded on one side and connected on its other side to a switch-testing device, adapted to be brought into connection with either line for testing, and a battery and test-bell in the circuit of said test-wire, substantially as and for the purpose set forth.

3. In a telephone-exchange system, the combination of two metallic-circuit lines temporarily connected together for conversation, a test-circuit containing a test-receiving instrument and a test-battery, said test-circnit being electrically connected on one side of said instrument and battery with said lines when they are thus connected for conversation, and then only, a test-bolt connected to said metallic circuit, and a switching device connected to said test-circuit on the other side of said instrument and battery,adapted at the will of the operator to be brought into electrical connection with said test-bolt, substantially as and for the purpose set forth.

4. Infa telephone-exchange system,1netalliccircuit lines normally disconnected from the ground, two or more switch-boards, to each of which the lines are connected, and switching devices at each board adapted to temporarily connect any two of the lines together for conversation, and when they are thus connected to ground their circuit, in combination with test-receiving instruments, one at each board, grounded on one side, switclrtesting devices at each board adapted at the will of the oper ator to connect its test-receiving instrument on the other side to the circuit of any line for testing, and a battery in the test-circuit thus established, substantially as and for the purpose set forth.

5. In a telephone-exchange system, the combination of metallic circuit lines, two or more switch-boards for said lines, test-circuits, one at each board, each test-circuit containing a test-receiving instrument and a test-battery, said test-circuits being electrically connected on one side to their test-receiving instruments and test-batteries, and normally disconnected from said" lines, switching devices at each board adapted to connect any two of said lines together for conversation and to connect them temporarily or when thus connected electrically with said test-circuits on said side of their test-receiving instruments and batteries, testbolts, one for each line on each board, each test-bolt being connected to its line when it is bolts at heroboard, substantially as and for the switched for conversation, and Switch-testing purpose'setforth; devices at each board, each connectedto the a test-circuit at its board on the other side of Q 5 the test-receivin g instrument and battery, and Witnesses:

adapted at the willof the operator to be brought PETER H. WITT,

' into electrical connection with any of the test- OAININ DE WOLF.

MILO G, KELLOGG. 

